Well 454 stops with 360 grain bullets.
Larger caliber, and heavier bullets, historically, just are MUCH more effective. The precedent for this is the considerable increase in killing and stopping power when bullet weight goes up from the 300 grain H&H loads, to the 500 grain 458 Lott/NE 450 loads.
One kills well, the other stops. While we can't get a real stopper in a pistol, the 525 grain bullets, at 1550 fps, or even at 1100 fps, will kill like a 375, and, will smash a big, straight hole, through most any game animal.
454's penetrate about 38" of Cape buffalo, with 350 grain LFNs. 475 and 500's will do near 60", or more, with less chance of being deflected from target line, with 420 grain, and 525 grain bullets. The difference between 3 feet of penetration in a DGA, and 5 or 6 feet, or more, is HUGE, if it's coming at you. Think of a charging brown bear. It weight about as much as 4-5 pro football defensive linemen, and, runs about 3 times as fast, with giant claws, and jaws, and, it's probably smarter then the linemen put together, as well.
To kill it, you need a big, long, hole, through vital areas, breaking bones. Not to mention you have to get through it's armour plating, of hair, mud, very thick skin, inside fat layer, and bones. Brown bears have taken successive shots from 375's. Two around here took 11 rounds of 375 H&H to finally go down. Another on Buffalobores site took a round from a 375, and from a 458 Lott, and took off running. My point is simply sometimes, you need as much gun as you can get.
Also, the power of some of these huge hollowpoints is something to see.
Friend shot a good sized deer, in the ham, going forward. NON-LETHAL shot placement. Deer should have, and with most calibers, would have run off, and recovered. The 400 grain, Hornady XTP hollowpoint expanded, and cut a huge hole through the ham. Didn't catch an artery, or anything, but, the deer ran 30 yards, and died. VERY STRANGE.
Others have noticed a killing power in these huge caliber revolvers that find their only precedent in the same factor occuring in rifle calibers.
Using the 454 as an upper limit denies about 100 years of ballistics, in large game hunting, that has clearly shown, that between 1000 fps, and 2500 fps, there is a HUGE difference in effect created by increasing bullet weight from 300 grains to 500, or more, grains.
I'd think of the 454 as the 375 H&H of pistols, with the 475 and 500 as the 450 Nitro Express 2, and the 500 Nitro Express of the pistol world..
If you have a choice, why not get the heavier caliber? Recoil and expense come to mind.
However, your initial strategy, that if the 454 won't get it done, you need a rifle, is sound...
Keep in mind, I was on the edge of the heavy 45 colt evolution, from about 1980 on, and, have one of the first
built 45 Colt/Linebaugh/Sevilles, capable, of killing Cape buffalo, etc.
Ross Seyfried did that with a sister gun to mine, and, his
response was to ask for the 475, or 500, and, to design the 585 Nyati affordable stopping rifle. I think that says it all, right there.
Something about having 1400 pounds of cape buffalo charging from 25 yards, and having no place to go, and having it die about 2 feet from you, after soaking up 6 shots of 345 grain, 1550 fps 45 colt rounds, that makes you think you might be lucky, as well as good, and, the next time, you might NOT be so lucky.
S